Magnesium base alloy



Patented June 16, 1942 MAGNESIUM BASE ALLOY John C. McDonald, Midland, Mlch., assignor to The Dow Chemical Company, Midland, Micln, a corporation of Michigan No Drawing. Application December 23, 1940,

Serial No. 371,373

3 Claims. (Cl. 75-168) The invention relates to magnesium base alloys and more particularly concerns an alloy of this nature having high yield and tensile strengths together with good formability or ductility.

Magnesium base alloys are being widely used in the structural art where a light weight metal is highly desirable. such as for use in making castings, forgings, and the like. However, the use. of these alloys in the rolled form to make sheet metal articles requiring forming operations, such as bending, drawing, and the like,

cerium is present in an amount of from 0.1 to 0.7 per cent, manganese in 1.5 to 2.5 per cent, and thallium from 3 to 8 per cent. A particularly desirable composition consists of 0.4 per cent cerium, 2 per cent manganese, andv per cent thallium, the balance being. magnesium.

The following table listing some of the properties of rolled sheet metal made from my new has not progressed as rapidly due to the fact that, in general, alloys having good formability or ductility permitting relatively sharp bends to be made without the article developing external cracks, usually have inferior characteristics as regards their tensile and yield strengths.

quaternary alloy and comparing these properties with those of related. alloys illustrates the improvement in yield and tensile strengths of my new alloy over that of related alloys and, at

the same time, shows the alloy to have satisfac-.

tory ductility or formability characteristics. In the table the per cent elongation is to be regarded. as a measure-of the ductility or formability of the alloys.

Table Nominal compog; t Annealed Cold rolled remainder) Percent Yield Tensile Yield Tensile Ce Mn 'll elongation strength in strength in strength in strength in in 2 inches lbs./sq.in. lbs./sq.in. lbs /sq.in lbs./sq.i n.

It is, accordingly. the principal object of the invention to provide a magnesium base alloy which can be made into rolled sheet and the like possessing a suflicient degree of ductility at ordinary temperatures to be sharply bent, drawn, or otherwise shaped while having highly improved tensile and yield strengths.

Other objects and advantages will be apparent as the description of the invention proceeds.

My invention resides in the discovery that magnesium base alloys containing from 0.01 to 1' per cent of cerium, 0.01 to 3 per cent of manganese and from 1'110 12 per cent of thallium possess the aforementioned desirable properties. The term magnesium used herein and in the appended claims is intended to include magnesium containing the ordinary impurities found in the commercially pure metal, such as traces of iron, copper, nickel, and silicon. While the properties of satisfactory ductility associated with highly improved tensile and yield strengths are manifest over the entire range of the compositions indicated, I have found that, in general, a preferred composition range is that in which The properties set forth above under the term annealed were obtained by first rolling the alloys at a temperature of 600 F. and thereafter annealing them at various temperatures through a range of from 400 to 800 F. The properties selected for the table were those of the annealed specimens which exhibited the maximum elongation. The properties set forth under the term "cold rolled were obtained by subjecting specimens of the alloys which had first been hot rolled at a temperature of 600? F. to additional rolling in the cold stage. The properties selected for the table were those of the cold rolled specimens whichshowed the greatest tensile and yield strengths, while having at least a 1 per cent elongation in 2 inches.

A comparison of the properties listed in the table shows that the tensile and yield strengths of. my new quaternary alloy are superior to those of related alloys in both the annealed and cold rolled condition. At the same time it will be noted that the per cent elongation which, serves as-a measure of the ductility or formability is of a sufficiently high order to. permit bending and forming operations to be readily carried out. Improvement shown in the particular composition set forth in the table is exhibited throughout the percentage range of alloying ingredients indicated.

While the new alloy is most useful in wrought form, such as sheets, due to its high yield and tensile strengths associated with satisfactory formability characteristics, it may also be used for making castings, extruded forms and the like.

The new alloy may be compounded by any of the methods usually employed for melting and alloying metals with magnesium, such as by adding the alloying ingredients singly or jointly to a bath of molten magnesium which is preferably protected from oxidation by suitable flux. Cerium may be added to the alloy as such, or in the form of Misch-metal. Magnesium-cerium alloys are commonly made up by employing Misch-metal as a source of cerium. It is sometimes desirable to add more than the theoretical amount of Misch-metal since the alloying efficiency is not always 100 per cent and some loss may be incurred.

It is to be understood that the invention is not limited to the specific composition herein described, but may taken other forms without departing from the scopeof the invention.

I claim:

1. A magnesium base alloy containing from 0.01 to 1 per cent of cerium, from 0.01 to 3 per cent of manganese and from 1 to 12 per cent of thallium, the balance being magnesium.

2. A magnesium base alloy containing from 0.1 to 0.7 per cent of cerium, from 1.5 to 2.5 per cent'of manganese, and from 3 to 8 per cent of thallium, the balance being magnesium.

3. A magnesium base alloy composed of 0.4 per cent of cerium, 2 per cent of manganese, and 5 per cent of thallium.

JOHN C. MCDONALD. 

